Ferrous base alloys



Oct. 20, 1959 F. M. RICHMOND ETAL 2,909,426

FERROUS BASE ALLOYS Filed March 27, 1958 :1, a Q Q \9 so v? ULTIMATE STRENGTH l 3 0 Alloy B A AII0 y 1 a; IAIloy H X Alloy G l O |0o I000 n00 I200 I300 I400 I500 Temperature, "F

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I20 8 x fil': -=r: A g W M 9 8O v," 0.2% YIELD STRENGTH t u; .Alloy B AAIIoy F Alloy H X A y e 40 I O I0 0 I000 II00 I200 I300 I400 lNvEzlggRs Temperaure OF Francis MpRichmofnl W I' J. enn'n on F! g. 2 Rb' r r' w Koff le r THEIR ATTORNEYS United States Patent \FERROUS BASE ALLOYS Francis'M. Richmond, William J. Pennington, and Robert W. Kofller, Pittsburgh, Pa., assignors to Universal- Cyclops Steel Corporation, Bridgeville, Pa., a corporation of Pennsylvania Application March 27, 1958, Serial No. 724,384

6 Claims. (Cl. 75-128) in many other fields in which various metallic parts areff subjected to appreciable loads at high temperatures. In"- the missile field, there are many applications for alloys] of this type due to the temperature and strength requirements. In addition, these alloys are useful in high pressure steam turbines, valve seats, exhaust valves and many other parts because of the fact that, in use, they, aref subjected to substantial loads at elevated temperatures.

The increased use of alloys having high strength at elevated temperatures has developed requirements that specify minimum strength as determined by the stress rupture life of the material. Some'of the alloys of this type which have been produced commercially have given erratic stress rupture properties with many values below those acceptable for the particular application. It has not been unusual to obtain extremely low, as well as reasonably satisfactory stress rupture properties on products from the same heat, thus making the application of such material questionable. Generally, where such varying results are obtained, the entire heat must be scrapped because of the inadvisability of applying questionable material for such critical uses, as for parts in airplanes, jet engines and missiles. The rejection of material having such variable stress rupture properties has resulted in low yields and reduced production, making it extremely ditficult to meet delivery requirements.

rupture properties which are so far below the stress rup-' ture properties of the alloys of our invention as to place our alloys in an entirely different category despite composition similarities.

In the aircraft industry, as well as mother industries mentioned above, there has been a demand for alloys having higher stress rupture properties at elevated temperatures than those possessed by any of those heretofore available, and, consequently, one of the objects of our invention is the provision of an alloy which, without any material sacrifice of other properties, will meet these exacting requirements as to stress rupture values at high temperatures. Another object of our invention is to provide such an alloy which is capable of being melted in relatively large furnaces, cast into large ingots and wrought by forging or rolling into the desired shapes and sizes. Some of the parts for alloys of the character involved here are complicated and require a high degree of accuracy and, consequently, one of the objects of our invention is to provide an alloy which is capable of being wrought to the desired size and shape. 7

We have discovered that astonishingly high stress rupture properties can-be obtained in ferrious base alloys of 2,909,426 Patented Oct. 20, 1959 vide superior tensile and yield strength at elevated temperatures. As will be shown hereinafter, the alloys of our invention possess outstanding properties as com.- pared with those of alloys having compositionswhich quite closely approximate the alloys'ofthis' invention. The alloys of this invention are precipitation hardenable by heat treatment alone and do not require any special processing, such as hot cold-working, to bring about the desirable properties and they can be made by vacuuminduction melting or by any of the other commercial methods, such as in an air-arc furnace, an air-induction furnace, a vacuum-arc furnace and the like. We have also found that, after melting and casting, the cast product can be forged or otherwise worked into suitable V shapes.

The ferrous base alloys of this invention contain nickel,

conium, boron and carbon, and these elements should 7 be present in about the amount specified in the following examples:

Alloy A Percent Carbon 0.098 Nickel 25.10 Chromium 16.20 Titanium 4.28 'Colurnbium and tantalum 0.49 Zirconium i "0.03 Boron 0.0022 Iron Balance Alloy B Percent Carbon 0.086 Nickel 25.28 Chromium 15.94 Titanium 4.12 Oolumbium and tantalum 0.58 Zirconium 0.02

Boron 0.0032 Iron Balance Alloy C Percent Carbon 0.076 Nickel 24.00 Chromium 15.24 Titanium 4.17 Columbium and tantalum 0.62 Zirconium 0.018 Boron 0.0873

Iron Balance Alloy D Percent Carbon 0.078 Nickel 24.56 Chromium 15.18 Titanium 4.39 Columbium and tantalum 0.50 Zirconium 0.017

Boron 0.1395 Iron Balance Alloy E Percent Carbon 0.075 Nickel 25.50 4 Chromium 16.32 Titanium 3.87 Columbium and" tantalum 0.88

Zirconium 0.067 Boron 0.0016 Iron Balance 4 Some departure from the specific percentages of the elements specified for Alloys A, B, C, D and B may be permitted without departing from this invention and without material sacrifice of the outstanding properties mentioned hereinafter. However, in order to obtain the surprising physical properties mentioned hereinafter, it has been found necessary to adhere fairly closely to the values set forth above.

In addition to the. elements mentioned above as being embodied in our alloys, they may contain small amounts of other elements frequently embodied in alloys of this general class such, for example, as aluminum, manga- 4 to 300 times greater than Alloys F, G and H which are representative of other alloys intended for the same applications.

The superior strength of our alloy is further demonstrated by comparing the stress rupture properties thereof with those of alloys of similar composition when tested at a temperature of 1350 F. and a load of 65,000 pounds per square inch. This comparison is set forth in Table II in which Alloys A, B, C, D and E are our alloys and other comparable alloys are designated as Alloys I to N, inclusive.

Table 11 Stress Alloy Ni Cr Ti Ob+Ta Zr B Rupture Life in Hrs nese, silicon, molybdenum, tungsten and vanadium. These elements, however, should not be present in any such amount as to adversely affect the stress rupture, tensile and yield strengths found to result from the alloys of the compositions specified above.

A comparison of our alloys and several alloys intended for the same applications as our alloys shows that our alloys possess stress rupture properties at 1200" F. and under a load of 65,000 pounds per square inch which place our alloys in an entirely different category. This comparison is set forth in Table I in which our alloys are Alloys A, B, C, D and E.

Table I In the foregoing table, it should be noted that Alloys A, B, C, D and E are quite similar to the other alloys shown therein except for certain variations in composition, yet, the average stress rupture life of our Alloys A, B, C, D and E is over 5 times as great as the average stress rupture life of the other alloys.

In Table HI, which is set forth below, we have shown a comparison between our alloys (Alloys A, B, C, D

and E) and the alloys intended for the same applications Stress Alloy 0 Ni Or Mo Al Ti Zr B Obi- Ta Other Rlzipltfsure in Hrs.

In the foregoing table, it should be noted that our Alloys A, B, C, D and E possess stress rupture lives 9 when subjected to stress rupture tests at 1350 F. and a load of 65,000 pounds per square inch.

Alloy 0 Ni Or Here again our alloys, Alloys A, B, C, D and E, show stress rupture lives 8 to over 200 times greater than Alloys F, G and H intended for the same applications.

In addition to the significantly higher stress rupture properties, our alloys exhibit superior ultimate tensile strength and yield strength at all temperatures as compared with the tensile and yield strengths of alloys intended for the same applications. This superiority is shown in the drawings, Figures 1 and 2.

In Figure 1, 'we have shown a comparison between the ultimate strengths of certain of the alloys intended to be used for the same type of application.

Figure 2 shows a comparison of the yield strength of Alloy B of our invention and the yield strengths of certain alloys intended to be used for the same type of application.

Both Figures 1 and 2 show data from room temperature up to 1500 F. It is quite apparent from the figures that Alloy B possesses considerably greater strength than similar alloys at temperatures above 1000 P.

All of the alloys set forth in Table II were melted in a vacuum-induction furnace. However, as stated above, our alloys may be melted by any of the other known commercial methods. After melting, our alloys are cast and may then be forged into suitable shapes employing the proper forging temperatures. Since our alloys attain their properties bysolution and precipitation hardening treatment, the proper solution and precipitation hardening treatment should be employed which will develop the maximum properties. Those treatments are well known in the art and need not be discussed herein.

As is apparent from those data set forth herein, the alloys of our invention possess properties which are so superior to the properties of somewhat similar alloys and alloys presently intended for the same purposes as to place our alloys in an entirely diiferent class. Our alloys possess great utility in the aircraft industry because they will permit significant increases in engine temperatures with the result that better engine perform ance can be achieved. Our alloys possess great utility in any application which requires a material having exceptionally high strengths at elevated temperatures.

While we have set forth five specific analyses of our alloys, it should be borne in mind that our invention is not limited to the specific values set forth, as some departures from the specific compositions may be made without adversely affecting the superior properties which evidently result from the synergistic effect of the alloying elements present in our alloys.

Our invention may be otherwise embodied within the scope of the following claims.

We claim:

1. A ferrous base alloy consisting essentially of about 0.075 to about 0.098% carbon, about 24.0 to about 25.5% nickel, about 15.18 to about 16.32% chromium, about 3.87 to about 4.39% titanium, about 0.49 to about 0.88% columbium and tantalum, about 0.017 to about 0.067% zirconium, and about 0.0016 to about 0.14% boron, the balance being iron.

2. A ferrous base alloy consisting essentially of about 0.098% carbon, about 25.1% nickel, about 16.2% chromium, about 4.28% titanium, about 0.49% columbium and tantalum, about 0.03% zirconium, and about 0.0022% boron, the balance being iron.

3. A ferrous base alloy consisting essentially of about 0.086% carbon, about 25.28% nickel, about 15.94% chromium, about 4.12% titanium, about 0.58% columbium and tantalum, about 0.02% Zirconium, and about 0.0032% boron, the balance being iron.

4. A ferrous base alloy consisting essentially of about 0.076% carbon, about 24.0% nickel, about 15.24% chromium, about 4.17% titanium, about 0.62% columbium and tantalum, about 0.018% zirconium, and about 0.0873% boron, the balance being iron.

5. A ferrous 'base alloy consisting essentially of about 0.078% carbon, about 24.56% nickel, about 15.18% chromium, about 4.39% titanium, about 0.5% columbium and tantalum, about 0.017% zirconium, and about 0.1395 boron, the balance being iron.

6. A ferrous base alloy consisting essentially of about 0.075% carbon, about 25.5% nickel, about 16.32% chromium, about 3.87% titanium, about 0.88% columbium and tantalum, about 0.067% zirconium, and about 0.0016% boron, the balance being iron.

References Cited in the file of this patent UNITED STATES PATENTS 2,750,283 Loveless June 12, 1956 

1. A FERROUS BASE ALLOY CONSISTING ESSENTIALLY OF ABOUT 0.075 TO ABOUT 0.098% CARBON, ABOUT 24.0 TO ABOUT 25.5% NICKEL, ABOUT 15.18 TO ABOUT 16.32% CHROMIUM ABOUT 3.87 ABOUT 4.39% TITANIUM, ABOUT 0.49 TO ABOUT 0.88% COLUMBIUM AN DTANTALUM, ABOUT 0.017 TO ABOUT 0.067% ZIRCONIUM, AND ABOUT 0.0016 TO ABOUT 0.14% BORON, THE BALANCE BEING IRON. 